Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$219.81	12.566%	$247.4313	$247.43	$247.45	$247.40
Purchase #2	$211.94	7.399%	$227.6214	$227.62	$227.60	$227.60
Purchase #3	$212.86	3.162%	$219.5906	$219.59	$219.60	$219.60
Purchase #4	$110.80	13.275%	$125.5087	$125.51	$125.50	$125.50
Purchase #5	$58.29	12.295%	$65.4568	$65.46	$65.45	$65.50
Purchase #6	$110.36	6.835%	$117.9031	$117.90	$117.90	$117.90
Purchase #7	$133.28	8.337%	$144.3916	$144.39	$144.40	$144.40
7 purchase totals =	$1,057.34		$1,147.9035	$1,147.90	$1,147.90	$1,147.90